<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>购物车全选</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        .wrap {
            width: 300px;
            margin: 100px auto 0;
        }
        table {
            border-collapse: collapse;
            border-spacing: 0;
            border: 1px solid #c0c0c0;
            width: 300px;
        }
        th,
        td {
            border: 1px solid #d0d0d0;
            color: #404060;
            padding: 10px;
        }
        th {
            background-color: #09c;
            font: bold 16px "微软雅黑";
            color: #fff;
        }
        td {
            font: 14px "微软雅黑";
        }
        tbody tr {
            background-color: #f0f0f0;
        }
        tbody tr:hover {
            cursor: pointer;
            background-color: #fafafa;
        }
    </style>
</head>
<body>
<div class="wrap">
    <table>
        <thead>
        <tr>
            <th>
                <input type="checkbox" id="j_cbAll" />
            </th>
            <th>商品</th>
            <th>价钱</th>
        </tr>
        </thead>
        <tbody id="j_tb">
        <tr>
            <td>
                <input type="checkbox" />
            </td>
            <td>iPhone8</td>
            <td>8000</td>
        </tr>
        <tr>
            <td>
                <input type="checkbox" />
            </td>
            <td>iPad Pro</td>
            <td>5000</td>
        </tr>
        <tr>
            <td>
                <input type="checkbox" />
            </td>
            <td>iPad Air</td>
            <td>2000</td>
        </tr>
        <tr>
            <td>
                <input type="checkbox" />
            </td>
            <td>Apple Watch</td>
            <td>2000</td>
        </tr>
        </tbody>
    </table>
</div>
<script>
    var j_cbAll = document.getElementById('j_cbAll'); 
    var j_tbs = document.getElementById('j_tb').getElementsByTagName('input');

    j_cbAll.onclick = function() {
        
        for (var i = 0; i < j_tbs.length; i++) {
            j_tbs[i].checked = this.checked;
        }
    }
    for (var i = 0; i < j_tbs.length; i++) {
        j_tbs[i].onclick = function() {
            var flag = true;
            for (var i = 0; i < j_tbs.length; i++) {
                if (!j_tbs[i].checked) {
                    flag = false;
                    break; 
                }
            }
            j_cbAll.checked = flag;
        }
    }
</script>
</body>
</html>